1. Technical Field
The present disclosure relates to a surgical instrument assembly for use in excising body tissue from an internal body cavity, and more particularly to a snare device for removing polyps.
2. Background of Related Art
Colonoscopic polypectomy is a commonly used method for removing and optionally retrieving polyps from the colon. Such operations are performed so that the polyps can be examined by a pathologist for malignancy. Devices for such removal and retrieval of tissue are disclosed and described in U.S. Pat. Nos. 5,486,182, 5,336,227, 5,201,740 and 5,190,542, to Nakao et al.
Typically, a snare device is used which has a distal loop of wire which can be inserted into the colon and positioned around the base of the polyp. Thereafter, the loop is closed around the stalk of the polyp to sever the tissue.
One complication which can develop with simple mechanical excision of the polyp is excessive bleeding. In order to reduce the amount of bleeding that can result from severing the polyp from its stalk some surgical apparatus employ an electrocautery snare. The electrocautery device can be monopolar as disclosed for example in U.S. Pat. No. 5,158,561, or bipolar as disclosed for example in U.S. Pat. Nos. 5,026,371 and 4,905,691. Monopolar devices generally use radio frequency ("rf") current.
Nevertheless complications can occur during electrocautery polypectomy procedures. For example, colonic perforation can result from the electrocautery current travelling via blood vessels to the base of the polyp and the wall of the colon, from the current travelling through the head of the polyp to the opposite wall, and from the accidental contact of the active electrode with surrounding tissue. Also, unobserved damage can occur from microperforations of the bowel wall and from pooled body fluids which contact the electrified wire and carry the current along unintended pathways to locations outside the field of view.
There yet remains a need for a polypectomy snare which provides the advantage of tissue cutting and coagulation while avoiding the disadvantages of electrocautery current.